Decoding device, imaging system, decoding method, coding/decoding method, and computer-readable recording medium

Abstract

A decoding device includes: a data obtaining unit configured to obtain a key block and a non-key brock, the key block forming a part of image data of one frame, and the non-key block forming a part of the image data of one frame on at least a part of which a coding process is performed; a characteristic information storage unit configured to store characteristic information regarding a pixel value correlation characteristic in a frame; and a decoding unit configured to perform repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before the coding process, the first log-likelihood being obtained from the non-key block, and the second log-likelihood ratio being obtained from the key block and the characteristic information.

What is claimed is: 
     
         1 . A decoding device configured to decode image data coded by an imaging device, the decoding device comprising:
 a data obtaining unit configured to obtain a key block and a non-key brock, the key block forming a part of the image data of one frame generated by the imaging device, and the non-key block forming a part of the image data of one frame generated by the imaging device on at least a part of which a coding process is performed;   a characteristic information storage unit configured to store characteristic information regarding a pixel value correlation characteristic in a frame; and   a decoding unit configured to perform repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before the coding process, the first log-likelihood being obtained from the non-key block on at least a part of which the coding process is performed, and the second log-likelihood ratio being obtained from the key block and the characteristic information stored in the characteristic information storage unit.   
     
     
         2 . The decoding device according to  claim 1 , wherein
 the characteristic information storage unit is configured to store a plurality of pieces of different characteristic information and   the decoding device is configured to change the second log-likelihood ratio to a second log-likelihood ratio obtained from the key block and the characteristic information different from the previously used characteristic information out of the plurality of pieces of characteristic information and re-perform the repeated decoding by using the changed second log-likelihood ratio.   
     
     
         3 . The decoding device according to  claim 1 , wherein the decoding unit is configured to perform the repeated decoding in a forward direction and the repeated decoding in a trace back direction, the repeated decoding in the forward direction being the repeated decoding performed based on the first log-likelihood ratio and the second log-likelihood ratio obtained from the key block obtained immediately before the non-key block in chronological order by the data obtaining unit and the characteristic information, and the repeated decoding in the trace back direction being the repeated decoding performed based on the first log-likelihood ratio and the second log-likelihood ratio obtained from the key block obtained immediately after the non-key block in chronological order by the data obtaining unit and the characteristic information. 
     
     
         4 . The decoding device according to  claim 3 , further comprising:
 an error detecting unit configured to detect whether there is an error by performing parity check on the non-key block estimated after the repeated decoding by the decoding unit, wherein   the decoding unit is configured to output the non-key block estimated after the repeated decoding in the forward direction or the non-key block estimated after the repeated decoding in the trace back direction as a decoded result based on a detection result by the error detecting unit.   
     
     
         5 . The decoding device according to  claim 3 , wherein the decoding unit is configured to output the non-key block estimated after the repeated decoding in the forward direction or the non-key block estimated after the repeated decoding in the trace back direction as a decoded result based on a posteriori log-likelihood ratio of the non-key block restored by the repeated decoding in the forward direction and a posteriori log-likelihood ratio of the non-key block restored by the repeated decoding in the trace back direction. 
     
     
         6 . The decoding device according to  claim 1 , further comprising: a display determining unit configured to perform a process of determining whether the non-key block estimated after the repeated decoding by the decoding unit is made a display target. 
     
     
         7 . The decoding device according to  claim 6 , further comprising:
 the error detecting unit configured to detect whether there is an error by performing the parity check on the non-key block estimated after the repeated decoding by the decoding unit, wherein   the display determining unit is configured to perform the determining process based on a detection result by the error detecting unit.   
     
     
         8 . The decoding device according to  claim 6 , wherein the display determining unit is configured to perform the determining process based on a posteriori log-likelihood ratio of the non-key block restored by the repeated decoding by the decoding unit. 
     
     
         9 . The decoding device according to  claim 1 , wherein each of the key block and the non-key block is a pixel group on at least one line arranged in a row direction or a column direction in the frame. 
     
     
         10 . The decoding device according to  claim 1 , wherein
 the imaging device includes an imaging unit including an imaging element and a color filter on which a plurality of filter groups grouped according to wavelength bands of transmitted light is arranged in a specified format on a light receiving surface of the imaging element,   the imaging unit is configured to generate image data corresponding to incident light through the color filter and sort the image data into the key block and the non-key block for each frame, and   the decoding unit is configured to group pixels included in the non-key block according to groups of the plurality of filter groups and perform the repeated decoding for each group.   
     
     
         11 . The decoding device according to  claim 1 , wherein
 the imaging device includes an imaging unit including an imaging element and a color filter on which a plurality of filter groups grouped according to wavelength bands of transmitted light is arranged in a specified format on a light receiving surface of the imaging element,   the imaging unit is configured to generate image data corresponding to incident light through the color filter and sort the image data into the key block and the non-key block for each frame,   the characteristic information storage unit is configured to store a plurality of pieces of characteristic information for each group of the plurality of filter groups, and   the decoding unit is configured to group the pixels included in the non-key block according to groups of the plurality of filter groups and perform the repeated decoding for each group by using the characteristic information corresponding to a group of the pixels on which the repeated decoding is performed out of the plurality of pieces of characteristic information stored in the characteristic information storage unit.   
     
     
         12 . An imaging system comprising:
 an imaging device configured to code image data generated by capturing an image of a subject to transmit, and   a decoding device configured to receive the coded image data to decode, wherein   the imaging device includes:
 an imaging unit configured to generate image data corresponding to incident light and sort the image data into a key block and a non-key block for each frame; 
 a coding unit configured to perform a coding process on at least a part of the non-key block; and 
 a transmitting unit configured to transmit the key block and the non-key block on at least a part of which the coding process is performed, and 
   the decoding device includes:
 a receiving unit configured to receive the key block and the non-key block on at least a part of which the coding process is performed; 
 a characteristic information storage unit configured to store characteristic information regarding a pixel value correlation characteristic for each color in a frame; and 
 a decoding unit configured to perform repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before coding process, the first log-likelihood being obtained from the non-key block on at least a part of which the coding process is performed, and the second log-likelihood ratio being obtained from the key block and the characteristic information stored in the characteristic information storage unit. 
   
     
     
         13 . The imaging system according to  claim 12 , wherein the coding process is syndrome coding using a parity check matrix. 
     
     
         14 . The imaging system according to  claim 12 , wherein
 the imaging unit includes:
 an imaging element; and 
 a color filter in which a plurality of filter groups grouped according to wavelength bands of transmitted light is arranged in a specified format on a light receiving surface of the imaging element, and 
   the coding unit is configured to group pixels included in the non-key block according to groups of the plurality of filter groups and perform the coding process by using a coding arithmetic matrix on at least a part of a group for each group, the coding arithmetic matrix used for at least one group out of the grouped plurality of groups being different from the coding arithmetic matrix used for other groups.   
     
     
         15 . The imaging system according to  claim 12 , wherein the imaging device is a capsule endoscope insertable into a subject. 
     
     
         16 . A decoding method executed by a decoding device configured to decode image data coded by an imaging device, the decoding method comprising:
 obtaining a key block and a non-key block, the key block forming a part of the image data of one frame generated by the imaging device, and the non-key block forming a part of the image data of one frame generated by the imaging device on at least a part of which a coding process is performed; and   performing repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before the coding process, the first log-likelihood being obtained from the non-key block on at least a part of which the coding process is performed, and the second log-likelihood ratio being obtained from the key block and characteristic information regarding a pixel value correlation characteristic in a frame.   
     
     
         17 . A coding and decoding method executed by an imaging system including an imaging device configured to code image data generated by capturing an image of a subject to transmit and a decoding device configured to receive the coded image data to decode, the coding and decoding method comprising:
 generating, by the imaging device, image data corresponding to incident light;   sorting, by the imaging device, the image data into a key block and a non-key block for each frame;   performing, by the imaging device, a coding process on at least a part of the key block;   transmitting, by the imaging device, the key block and the non-key block on at least a part of which the coding process is performed;   receiving, by the decoding device, the key block and the non-key block on at least a part of which the coding process is performed; and   performing, by the decoding device, repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before the coding process, the first log-likelihood being obtained from the non-key block on at least a part of which the coding process is performed, and the second log-likelihood ratio being obtained from the key block and characteristic information regarding a pixel value correlation characteristic for each color in a frame.   
     
     
         18 . A non-transitory computer-readable recording medium having an executable program recorded thereon, the program instructing a processor, which is included in a decoding device configured to decode image data coded by an imaging device, to execute:
 obtaining a key block and a non-key brock, the key block forming a part of the image data of one frame generated by the imaging device, and the non-key block forming a part of the image data of one frame generated by the imaging device on at least a part of which a coding process is performed; and   performing repeated decoding by a belief-propagation method based on a first log-likelihood ratio and a second log-likelihood ratio to estimate the non-key block before the coding process, the first log-likelihood being obtained from the non-key block on at least a part of which the coding process is performed, and the second log-likelihood ratio being obtained from the key block and characteristic information regarding a pixel value correlation characteristic in a frame.